1. Field of the Invention
The present invention relates to a band controller for controlling network bands, and more particularly, to a band controller for quenching buffer overflows that may occur during band control for UDP (User Datagram Protocol) traffic of TCP/IP protocol, its buffer overflow quenching method, and a storing medium for storing a buffer overflow quench controlling program.
2. Description of the Related Art
Along with the rapid spread of network utilization in every area of people""s activities, an increasing number of networks have come to be forced to carry different types of communication data created on various application programs, all at one time. Such a network is required to provide one guarantee band for each application, which has been met by controlling network bands using routers or other dedicated devices.
TCP/IP protocol, whose extensive use has been driven by the spread of the Internet, comprises TCP (Transmission Control Protocol) for providing connection-type communication services and UDP (User Datagram Protocol) for providing connectionless-type communication services, which together correspond to the transport layer of OSI (Open System Interconnection); either TCP or UDP is chosen for use as appropriate for a specific application. Examples of applications that use TCP include FTP, TELNET, and SMTP; those that use UDP include TFTP, SNMP, and NTP. Applications that conduct multicast to unspecified terminals, which has gained popularity rapidly in recent years, mainly use UDP.
FIG. 10 shows the format of TCP, and FIG. 11 shows the flow of communication processing via TCP. As shown in FIG. 11, in TCP, the transmitting side receives an acknowledgement (ACK) from the receiving side and then sends out packets to be transmitted. Some existing band controllers utilize this mechanism to use an ACK packet effectively, not simply to buffer packets, thereby achieving efficient control of traffic volumes.
FIG. 12 shows the format of UDP. In UDP, acknowledgement is not done by the protocol, but by each application as necessity arises. Since the method of acknowledgement varies among different applications, existing band controllers conduct band control for UDP through buffering only.
However, there is a limit to the capacity of any buffer, and thus a buffer overflow will be caused when the volume of traffic from the transmitting side exceeds the band limitation imposed by a band controller, leading to lost packets or occurrence of re-transmission. In the worst case, the user may even suffer a session timeout and consequent communication stoppage.
As described above, conventional band controllers have a drawback that they perform band control for UDP through buffering only. This often causes a number of problems to occur due to buffer overflows when traffic volumes from the transmitting side exceed the band limitations imposed by these controllers, including lost packets, occurrence of re-transmission, and abnormal end of communication.
An object of the present invention is to provide a band controller that can eliminate the above-mentioned drawback faced by conventional band controllers during UDP transmission, by quenching buffer overflows by sending a source quench message, one of the ICMP (Internet Control Message Protocol) messages, to the transmitting side to make it decrease its own transmission rate directly before UDP traffic causes a buffer overflow; its buffer overflow quenching method; and a storing medium for storing a buffer overflow quenching program.
According to the first aspect of the invention, a band controller installed on a network for performing band control, comprises
a band setting means for setting a band for UDP traffic through own device,
a frame generating and analyzing means for directing the transmitting-side device to decrease the transmission rate from the transmitting-side device, by analyzing the transmission rate of UDP traffic over the network; calculating the buffer utilization rate in buffering that occurs if the transmission rate obtained by analysis is greater than the band set on the band setting means, generating a source quench message, one of the ICMP messages, if the buffer utilization rate obtained by calculation is equal to or greater than the pre-determined buffer overflow critical utilization rate, and sending the source quench message to the transmitting-side terminal.
In the preferred construction, the band controller further comprises a storing means for storing the total capacity of buffers and the buffer overflow critical utilization rate in a re-writable manner, and wherein the frame generating and analyzing means calculates the buffer space used in own device, based on the band that has been set, the transmission rate that has been obtained through analysis, and transmission time for UDP traffic; calculates the buffer utilization rate from the buffer space used obtained by calculation and the total capacity of the buffers; compares the buffer utilization rate obtained by calculation with the buffer overflow critical utilization rate stored in the storing means, and sends out the source quench message.
In another preferred construction, the band controller further comprises a timing controlling means for controlling the timing of calculation of a buffer utilization rate and sending of the source quench message by the frame generating and analyzing means.
In another preferred construction, the frame generating and analyzing means sends out the source quench message after adding a request rate that shows the requested value to which the transmission rate should be decreased.
In another preferred construction, the frame generating and analyzing means sends out the source quench message repeatedly until the buffer utilization rate becomes equal to or below the buffer overflow critical utilization rate.
According to the second aspect of the invention, a buffer overflow quenching method performed by a band controller installed on a network for performing band control, comprising the steps of
analyzing the transmission rate of UDP traffic over a network,
calculating the buffer utilization rate in buffering that occurs if the transmission rate obtained by analysis is greater than the preset band,
generating a source quench message, one of the ICMP messages, if the buffer utilization rate obtained by calculation is equal to or greater than the pre-determined buffer overflow critical utilization rate, and sending the source quench message to the desired transmitting-side terminal.
In the preferred construction, the buffer overflow quenching method further comprises a storing means for storing the total capacity of buffers and the buffer overflow critical utilization rate in a re-writable manner, and comprising the steps of
calculating the buffer space used in own device, based on the band that has been set, the transmission rate obtained by analysis, and transmission time for UDP traffic, and calculating the buffer utilization rate from the buffer space used obtained from calculation and the total capacity of the buffers,
comparing the buffer utilization rate obtained by calculation with the buffer overflow critical utilization rate stored in the storing means, and sending out the source quench message.
In another preferred construction, the buffer overflow quenching method comprising the step of
sending out the source quench message repeatedly until the buffer utilization rate becomes equal to or below the buffer overflow critical utilization rate.
In another preferred construction, the buffer overflow quenching method comprising the step of
sending out the source quench message after adding a request rate that shows a requested value to which the transmission rate should be decreased.
According to another aspect of the invention, a computer readable memory storing a buffer overflow quench controlling program for preventing buffer overflows by controlling a band controller installed on a network for performing band control, wherein
the buffer overflow quench controlling program comprising the steps of
analyzing the transmission rate of UDP traffic over a network,
calculating the buffer utilization rate in buffering that occurs if the transmission rate obtained by analysis is greater than the preset band,
generating a source quench message, one of the ICMP messages, if the buffer utilization rate obtained by calculation is equal to or greater than the pre-determined buffer overflow critical utilization rate, and sending the source quench message to the desired transmitting-side terminal.
Other objects, features and advantages of the present invention will become clear from the detailed description given herebelow.